These were sold as mixed bantams - any idea what breeds?
I think they are probably multi-generation mixes, not just a cross of two pure breeds. So each one could easily be a mix of 4 or more breeds.
Since they are bantams, they must have at least some bantam ancestors, but they could also have some standard-sized breeds mixed in.
The black one has a crest. That means it has a parent with a crest, who in turn has a parent with a crest, etc. I think I see muff/beard on the face too, which would have the same kind of inheritance: must be present in one parent, and in one parent of that bird, and so forth.
Because of the crest, it might be part Polish bantam, or it could be part Silkie (not half Silkie, because it does not have feathered feet, but it could be 1/4 Silkie or 1/8 Silkie or something like that.) There are other options as well, including non-bantam ones.
Black is present in so many breeds, bantam and standard, that it's not even worth trying to guess which one is involved.
For the second one, it might be part Silver Laced Sebright, or it might be part Wyandotte Bantam (Silver Laced or Silver Columbian), or it might be part Delaware bantam, or a few other options. (These guesses are based on the color/pattern I'm seeing.)
If I wanted to make up a possible set of parents, the black could be something like Cream Legbar (standard size) x Black Old English Game Bantam, with the result crossed to a Mille Fleur d'Uccle x Blue Rosecomb. But I could be wrong about every one of those breeds, and there are many other sets of 4 or more breeds that can cause a chicken with the traits of the one you have.
If they lay eggs, the color of the eggs can tell a little bit about their ancestry, especially if the eggs are blue or green: that would mean they are some kind of Easter Egger. If the eggs are cream or brown, it doesn't tell much, because of how many breeds lay those colors. If the eggs are completely white, that would also tell something about what breeds are likely in their ancestry (although I can't immediately think of what breeds that would be.)